If you're a fan of mash-up then I've got the perfect site for you. In the late 90s DJs started to make a name for themselves by 'bootlegging' records, putting an a cappella vocal over an instrumental version of another famous track (my favourite being Mojo's Lady mixed with Brandy and Monica's The Boy is Mine - I don't know why but it just worked for me). This has moved right into the mainstream with the likes of Two Many DJs. Well now there's a pretty swish dutch website called Mash Culture that has regular new mash-ups to download, including some pretty cool mixes.
Also check out Mashing from 64-95 for some Lemon Jelly mashing.